Answers about conversion accuracy, decimal places, US and imperial gallons, live currency rates, embeddable widgets and how your data is handled.
Yes, and the factors fall into two kinds. Some are exact by definition — an inch is exactly 25.4 mm, a pound is exactly 0.45359237 kg — so those conversions carry no rounding at all. Others rest on measured or agreed values, such as the astronomical unit or the BTU, and are accurate to far more digits than the result displays. Every conversion runs in your browser rather than on a server, so nothing is lost in transit.
The precision adapts to the size of the number, because a fixed number of decimals would be useless at both ends of the scale. Results of 1 or more show two decimal places, values below 1 show four, and values below 0.01 show six. Anything above a quadrillion or below a millionth switches to scientific notation, and figures over a thousand gain thousands separators.
Both, listed separately as Gallon (US) and Gallon (UK), because they differ by about 20 percent and picking one silently would make the other wrong. The same applies to pints, quarts and fluid ounces throughout the volume converter. If a figure comes from a British source, choose the UK unit. Our guide to litres and gallons explains where the split came from.
Yes. Rates are fetched from a live feed and cached for five minutes, so repeated conversions do not re-request them. If the feed cannot be reached the converter falls back to a built-in set of reference rates and keeps working, though those will be out of date. For anything financial, confirm the rate with your bank or payment provider before relying on it.
Because temperature scales disagree about two things at once: how large a degree is, and where zero sits. Celsius and Fahrenheit differ by a factor of 1.8 in degree size and by a 32 degree offset, so both have to be applied. This is also why a temperature difference converts with the 1.8 alone and no offset — a 10 °C rise is an 18 °F rise, not 50 °F.
Because decibels are logarithmic rather than linear, so no single multiplier can be correct. Doubling sound pressure adds about 6 dB rather than doubling the number. Phons, sones and sound intensity each relate to sound pressure by a different curve, and the A-weighted and hearing-level units depend on frequency as well, so the sound category converts by formula rather than by factor. Our guide to the decibel scale covers why.
Because the two systems measure opposite things. Miles per gallon is distance per volume, so higher is better. Litres per 100 km is volume per distance, so lower is better. Converting between them inverts the relationship rather than scaling it, which is why an improvement in one shows up as a smaller number in the other. The same inversion applies to running pace against speed.
No — the converter handles it. It is worth knowing why the numbers look surprising, though. Since an inch is 2.54 cm, a square inch is 2.54 squared, or 6.4516 cm², and a cubic inch is 2.54 cubed, or 16.387 cm³. Applying the linear factor to an area understates it by more than 60 percent, which is the single most common error in area conversion.
Yes. The widgets page provides embeddable versions of several converters, including the unit converter, baking, currency, speed and world clock. Each one is a single snippet of code to paste into your page, and the widget matches the visitor's light or dark system theme automatically.
No. Conversions are calculated in your browser and the numbers you enter are never sent anywhere. The site does use Google Analytics, which sets its own cookies to measure traffic, and a cookie notice appears on your first visit. Full details are in the privacy policy, linked in the footer of every page.
Please do — corrections are welcome and get acted on. Use the contact page or email simpleunitconverter@hotmail.com, and include the units and the figure you expected. Several factors on the site have been corrected this way, so a report genuinely helps.
No more than your original measurement had. A conversion cannot create precision that was not in the input, so converting a room measured to the nearest centimetre into inches to four decimal places implies an accuracy you do not have. Round the answer back to roughly the precision you started with, as our guide to significant figures and rounding explains.